Refrigerator control



March 5, 19-40. R. w. HASTINGS REFRIGERATOR CONTROL Filed April 30, 1937 INVENTOR ROGER W.HAs-n-as.

ATTQRNEy Patented Mar. 5, 1940 PATENT OFFICE REFRIGERATOR. CONTROL Roger W. Hastings, Springfield, Mass., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 30, 1937, Serial No. 139,874

20 Claims.

My invention relates to refrigerating apparatus and has for an object to provide improved control means for such apparatus.

A further object of the invention is to maintain the temperature within a domestic refrigerator substantially constant regardless of changes in the temperature of the air in the room in which the refrigerator is located.

It is a further object of the invention to vary the temperature of the evaporator of a motordriven refrigerating machine in response to the load on the motor.

A- still further object of the invention is to vary the temperature of the evaporator of a motor-driven refrigerating machine in accordance with the heat load in the compartment cooled by the evaporator so as to maintain the air in the compartment at a substantially constant mean temperature.

These and other objects are effected by my invention, as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a diagrammatic view of a refrigerating machine controlled in accordance with the invention;

Fig. 2 is a sectional view taken in a vertical plane through the control mechanism shown in Fig. l and viewed from the same point as Fig. l; and

Figs. 3, 4, and 5 are sectional views of the control and are taken, respectively, along the lines III-III, IV-IV, and V-V, of Fig. 2.

Reference will now be had to Fig. 1 wherein. I have shown my invention applied to a domestic refrigerator having an insulated cabinet III defining a food storage compartment ll cooled by a suitable evaporator at l2. The latter may include shelf portions l3 for supporting trays ll in which fluid to be congealed may be disposed.

Refrigerant vaporized in the evaporator I3 is withdrawn through a suction conduit 15 by a compressor l6 driven by an electric motor H. The Withdrawn vapor is compressed to a relatively high pressure by the compressor l6 andis conveyed by a conduit [8 to a condenser 19, preferably air cooledby a fan 2| The vapor is cooled and condensed in the condenser l9 and the liquefied refrigerant is returned to the evaporator l2 by means of a conduit 22 having a suitable expansion device such as, for example, a high side float valve 23 connected therein.

The apparatus described heretofore defines a conventional refrigerating system of thecompressor condenser-expander type and, as the operation of such systems is well understood in the art, no further description is deemed necessary. The temperature of the evaporator I2 is maintained between desired limits by a control mechanism, shown at 24, which starts and stops operation of the motor I! and the compressor IS in response to predetermined high and low temperatures of the evaporator l2 The control mechanism 24 is constructed and arranged in accordance with my invention and a description of the same will now be given.

I have chosen for a description of the invention a control mechanism of the type shown and claimed in my copending application, Serial No. 139,873, filed April 30, 1937, and assigned to the Westinghouse Electric 3: Manufacturing Company. This type of control mechanism is shown by way of example and it is to be understood that my invention is equally applicable to other types.

Reference will now be had to Figs. 2 to 5, inclusive, of the drawing. The control mechanism 24 includes a casing 25 having suitable mounting cars 26 for attachment to the evaporator I2, a portion of which, is shown in Figs. 2 and 4. The casing 25 includes end walls 2'! and 28, the latter of which includes a flexible or movable portion shown as an expansible bellows 29. The casing 25 and bellows 29 define a hermetically sealed chamber 3| for housing a switch structure 32 and a thermo-responsive member or disk 33 for actuating the same. A pinch tube may be provided so that an inert gas may be admitted to the chamber 3!, whereby oxidation of the contacts is reduced and the capacity of the switch is thereby increased.

The switch structure 32 includes a stationary i contact 34 and a movable contact 35 cooperating therewith, the former being supported by a suit "able rigid conducting member 36 that extends through gas-tight insulating seals 31 in the wall 28. The movable contact 35 is carried by'a spring 38 that biases the contact 35 toward the stationary contact 34 and which includes laterally extendingsupportingportions 39. The latter are suitably secured to a conducting member 4| that passes through gas-tight seals 42 in the casing wall 28. The switch structure 32 is connected in the electrical circuit of the motor I! as described hereinafter for initiating and terminating operation thereof.

Dpening and closing of the switch structure 32 is in response to predetermined low and high temperatures of the evaporator l2 and, to this end, the thermal responsive member or bimetal where it quickly reflects the temperature thereof. A bimetal disk of the type shown snaps rapidly from one position to another in response to predetermined temperatures. As thermoresponsive members of this type are well known in the art, no further description of their operation is deemed necessary.

The disk 33 is secured at its periphery between the casing 25 and a guide plate 44 and the central portion of the disk carries a socketed fitting 45 that is slidably guided by the plate 44. Movement of the disk is'transmitted to the spring 38 and movable contact by an insulating yoke 46, the latter including an opening 41 through which the spring 38 extends. The yoke 46 is held within the socketed fitting by a spring 48 that engages the inner surface of the bellows 29, and which biases the thermal responsive disk 33 and switch structure 32 toward their switch open positions. As shown in Figure 4, the disk 33 is relatively warm and the switch 32 is closed. When the temperature of the disk 33 is depressed to a predetermined value, it snaps to the position shown in broken lines (Fig. 2). Rapid separation of the contacts 34 and 35 is effected as the side of the opening 41 engages the contact carrying spring 38 during this snapacting movement.

The control may be provided with an operators adjustment including a cam 49 against which the bellows 29 bears, a shaft 5| carrying the cam 49 and a handle or knob 52 for rotating the shaft. The shaft 5| is journaled in a cap or cover 53 that may be adjustably secured to the casing 25 by one or more screws 54. Rotation of the cam 49 increases or decreases the bias of the spring 48 and thereby increases or decreases both the upper and lower temperatures at which the disk 33 operates the switch.

In accordance with my invention, the temperature of the evaporator I2 at which the thermal disk 33 operates to open the switch 32 is varied in response to variations in temperature of the air exterior of the cabinet I III and to changes in the heat load in the compartment. When the temperature of the exterior air increases or when the heat load in the compartment I I is increased, the temperature of the evaporator I2 at which the disk 33 operates to open the switch is decreased. Conversely, the temperature to which .ture of the air surrounding the cabinet and to different heat load caused partly by variations in the amount and temperature of the food prod:

ucts in the compartment II. By varying the mean evaporator temperatures in response to the above-mentioned conditions, the temperature of the air in the food storage compartment is maintained substantially constant.

An increase in temperature of the air in the room causes an increased load on the compressor I 6 and motor II. This is due primarily to increased head pressure, especially in machines employing air cooled condensers. The load on the motor is also increased when the heat load is increased, because of the increased amount of high density gas that must be withdrawn from the evaporator by the compressor and condensed. The amount of current energizing the motor I1 7 is therefore increased with a rise in room temdisk 33 is disposed adjacent the evaporator I2 perature or heat load. I employ the value of energizing current consumed by the motor to vary the mean evaporator temperature maintained by the control. As shown, a heated element 55 is disposed in heat transfer relation with the disk 33 and may be energized in any suitable manner to a degree that bears a relation to the degree of energization of the motor I'I. Preferably, the heater 55 is connected in series with the motor IT. The terminal leads of the heater, shown at 56 and 51, may extend through gastight seals 58 in the casing 25 and are connected in the motor circuit.

The source of power-for the motor I! is shown by line conductors L1 and L2. One terminal of the motor is directly connected to the conductor L1, as shown in Fig. 1, and its other terminal is connected by a conductor 59 to the contact supporting conductor 4| (Fig. 3). A conductor BI extends from the other contact supporting conductor 36 to the terminal lead 56 of the heater 55 and the opposite heater lead 51 is connected to the line conductor L2 by means of a conductor 62. These connections define a circuit having the motor I1 and heater 55 in series and controlled by the switch 32.

Operation As shown in the drawing, the temperature of the evaporator I2 is above the value at which the disk 33 snaps to its circuit open position and the motor I! and heater 55 are energized. Circulation of refrigerant through the evaporator I2 is effected by the compressor I6 for cooling the same. Heat is imparted to the disk 33 by the heater 55 and is abstracted from the disk 33 by the evaporator I2. The amount of heat imparted to the disk 33 is a function of the energizing current of the motor I1 and the load thereon. As the load on the motor I1 is a function of room temperature or heat load, the amount of heat imparted to the disk 33 is also a function of these variables.

When the room temperature or heat load is relatively high, heat is imparted to the disk 33 at a high rate and it is, therefore, necessary for the compressor to operate to reduce the evaporator to a relatively low temperature before the disk operates to open the switch. During periods when the room temperature or heat load are relatively low, heat is imparted to the disk at a lower rate so that the disk operates to stop operation of the compressor at a higher evaporator temperature than during periods when these variables are relatively high.

During inactive periods of the compressor, the heater is deenergized so that the temperature at which the disk 33 closes the switch is substantially constant for a given setting of the adjusting cam 49. Accordingly, it is the lower temperature limit or the temperature at which the switch 32 is opened by the disk 33 and also the mean temperature of the evaporator that are changed by variable operating conditions.

From-the foregoing, it will be apparent that I have provided an improved control for a refrigerator in which the evaporator temperature is varied inversely with changes in temperature exterior of the refrigerated zone or changes in heat load so that compensation is effected for increased or decreased flow of heat to the evaporator.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not solimited, but is susceptible of various changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shali be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

i. In refrigerating apparatus, the combination or" an evaporator, a'compressor for circulating refrigerant through the evaporator, a motor for diving the compressor, a switch for controlling the operation of the motor, a device responsive to predetermined high and low temperatures of the evaporator for respectively closing and open-' ing the switch, and means responsive'to the load on said motor for varying the temperature at which said device operates to open the switch.

2. In refrigerating apparatus, the combination of an evaporator, a compressor for circulating refrigerant through the evaporator, a motor for driving the compressor, means responsive to the temperature .of the evaporator for controlling the operation of the motor, said means being operative to initiate and terminate operation of the motor in response to predetermined high and low temperatures orthe evaporator, respectively, and means responsive to the amount of current energizing the motor for varying the mean tempera ture at which the evaporator is maintained.

3. In refrigerating apparatus, the combination of an evaporator, a compressor for circulating re= frigerant through the evaporator, a motor for driving the compressor, means responsive to the temperature of the evaporator for controlling the operation of the motor, said means being operative to initiate and terminate operation of the motor in response to predetermined high and a low temperatures of the evaporator, respectively, and means responsive to the current of the motor for varying the temperature oi the evaporater at which the temperature-responsive means operates to terminate operation of the motor.

In refrigerating apparatus, the combination of an evaporator, a compressor for circulating refrigerant through the evaporator, a motor for driving the compressor, means respnsive to the temperature of the evaporator for controlling the operation of the motor, said means being operative to initiate and terminate operation of the motor in response to predetermined high and low temperatures of the evaporator, respectively, a heater disposed in heat transfer relation with said temperature-responsive means and means for automatically energizing the heater during operating periods ofthe motor, the value of the current energizing the heater being proportional to the value of the, current in the motor.

5. The combination as claimed in claim 4 wherein the motor and the heater are connected in series.

6. in refrigerating apparatus, the combination of an evaporator, means for circulating refrigerant through the evaporator, means responsive to the temperature of said evaporator for controlling, the operation of the refrigerant circulating means, an relectrical heater disposed in heat transfer relation with the temperature responsive means, and means responsive to the heat load on said evaporator for controlling the degree of energization of said heater.

'7. In refrigerating apparatus, the combination of means defining a compartment to be cooled, an evaporator disposed for cooling the compartment, a compressor for circulating refrigerant through the evaporator, a motor for driving the compressor, a thermostat responsive to predetermined high and low temperatures of the evaporator for initiating and terminating operation of said motor and means responsive to the temper:

ature of the atmosphere exterior of the compartment for varying at least one of the temperatures to which said thermostat responds, said last-mentioned means including a heater disposed in heat transfer relation with the thermostat and connected to said motor so that it is energized therewith, the degree \of energization being proportional to the load on the'motor.

8.'In refrigerating apparatus, the combination with means defining a zone to be cooled, an evaporator for cooling the zone, a compressor for circulating refrigerant through the evaporator and a motor for driving the compressor, of means for controlling the operation of the motor including a casing structure secured to the evaporator and defining a hermetically sealed chamber, a thermal responsive device disposed within the chamber and in heat transfer relation with the evaporator, a switch for controlling the operation of the motor and actuated in a snap-acting manner by the device, said switch being disposed within said hermetically sealed chamber, and an electrical heater'disposed in heat transfer relation with the device and controlled by the switch, said heater being energized during operating periods of the motor and to a degree that bears a predetermined relation to the degree of energization of the motor and the load thereon.

9. In refrigerating apparatus, the combination with means defining a zone to be cooled, an evaporator for cooling the zone, a compressor for circulating refrigerant through the evaporator and a motor for driving the compressor, of means for controlling the operation of the motor including' a casing structure secured to the evaporator and defining a hermetically sealed chamber, a thermal responsive device disposed within the chamber and in heat transfer relation with the evaporator, a switch for controlling the operation of the motor and actuated in a snap-acting maner by the device, said switch being disposed within said hermetically sealed chamber, means manually operated at will for varying the temperatures at which said switch is actuated by the thermal responsive device, and an electrical heater disposed in heat transfer relation with the thermal responsive device and energized during operating periods of the motor to a degree that bears a predetermined relation to the energizing current of the motor.

10. In refrigerating apparatus, the combination of means defining a compartment to be cooled, an evaporator disposed for cooling the compartment, a compressor for circulating refrigerant through the evaporator, a motor for driving the compressor, a thermostat responsive to predetermined high and low temperatures of the evaporator for initiating and terminating operation of said motor, an electrically energized heater disposed in heat transfer relation with the thermostat, means responsive to the heat load on said evaporator for varying the degree of energization of said heater whereby one of said temperatures to which the temperature responsive means operates is varied, and manually operated means for adjusting, at will, both of the temperatures to which the temperature responsive means responds.

ll. Ina thermostatic switch structure f r controlling the operation of a refrigerator including dill a refrigerated cabinet and a refrigerating system, said refrigerating system including an evaporator disposed in the refrigerated cabinet, the combination of a switch, temperature-responsive means for actuating the switch, separate means effective to modify-the action of the temperature-responsive means in response to changes in refrigeration load, and means for retaining the switch, temperature-responsive means and modifying means in closely spaced operative relation as a single package within the refrigerated cabinet.

12. In a thermostatic switch structure for controlling the operation of a refrigerator including a refrigerated cabinet and a refrigerating system,- said refrigerating system including an evaporator disposed in the refrigerated cabinet and having refrigerant inlet and outlet pipes leading to the evaporator, the combination of a switch, temperature-responsive means for actuating the switch, separate means effective to modify the action of the temperature-responsive means in response to changes in refrigeration load, and means for retaining the switch, temperatureresponsive means and modifying means in closely spaced operative relation as a single package within the refrigerated cabinet,-said retaining means being arranged so as to be supported from and adjacent to the evaporator as distinguished from said inlet and outlet pipes and being effective to transmit heat between the evaporator and the temperature-responsive means.

13. In a thermostatic switch structure for controlling the operation of a refrigerator including a refrigerated cabinet and a refrigerating system, said refrigerating system including an evaporator disposed in the refrigerated cabinet, the combination of a switch, temperature-responsive means for actuating the switch, separate means effective to modify the action of the temperatureresponsive means in response to changes in refrigeration load, a casing for enclosing the switch and temperature-responsive means and for retaining the switch, temperature-responsive means and modifying means in closely spaced operative relation as a single package Within the refrigerated cabinet, said casing being so arranged as to be supported adjacent to the evaporator and being effective to transmit heat between the evaporator and the temperature-responsive means.

14. In a thermostatic switch structure for controlling the operation of a refrigerator including a refrigerated cabinet and a refrigerating system, said refrigerating system including an evaporator disposed in the refrigerated cabinet and having refrigerant inlet and outlet pipes leading to the evaporator, the combination of a switch, separate means automatically effective to modify the action of the temperature-responsive means in response to changes in refrigeration load, and a casing for enclosing and supporting the switch, temperature-responsive means and modifying means in closely spaced operative relation as a single package within the refrigerated cabinet, said casing being so arranged as to be supported adjacent to the evaporator and being effective to transmit heat between the evaporator and the temperature-responsive means.

15. In a thermostatic switch structure for controlling the operation of a refrigerator including a refrigerated cabinet and a refrigerating system, said refrigerating system including an evaporator disposed in the refrigerated cabinet, the combination of a switch, temperature-responsive means for actuating the switch, separate means effective to modify the action of the temperature-responsive means in response to changes in refrigeration load, means for retaining the switch, temperature-responsive means and modifying means in closely spaced operative relation as a single package within the refrigerated cabinet, said retaining means being effective to transmit heat between the evaporator and the temperature-responsive means, and manually adjustable means for varying the temperatures at which the temperature-responsive means actu-- ates the switch.

16. In a thermostatic switch structure for controlling the operation of a refrigerator including a refrigerated cabinet and a refrigerating sys tem, said refrigerating system including an evaporator disposed in the refrigerated cabinet, the combination of a switch, temperature-responsive means for actuating the switch, switch-operating mechanism disposed between the temperatureresponsive means and the switch, separate means effective to modify the action of the temperatureresponsive means in response to changes in refrigeration load, andmeans for retaining the switch, switch-operating mechanism, temperature-responsive means and modifying means in closely spaced operative relation as a single package within the refrigerated cabinet, said retaining means being so arranged as to be supported adjacent to the evaporator and being effective to transmit heat between the evaporator and the temperature-responsive means. 17. In refrigeration apparatus, the combination of a heat-insulated cabinet, a cooling element for abstracting heat from the cabinet, refrigerantsupplying means for said cooling element and thermostatic means for controlling the operation of the refrigerant-supplying means, said thermostatic means being entirely disposed within said cabinet and including a thermal-responsive element and a switch actuated by the element, means for substantially enclosing said switch, and means associated with and carried by said enclosing means for automatically adjusting the thermal-responsive element in response to changes in refrigeration load so as to maintain a substantially constant temperature in said cabinet.

18. In a thermostatic switch structure for controlling the operation of a refrigerator including 4 a refrigerated cabinet and a refrigerating system,

said refrigerating system including an evaporator disposed in the refrigerated cabinet, the combination of a switch, temperature-responsive means for actuating the switch, means for modifying the action of the temperature-responsive means comprising a heater disposed in heat conducting relation with the temperature-responsive means and having its heat output varied by changes in refrigeration load, a casing for enclosing the switch and temperature-responsive means and for retaining the temperature-responsive means and modifying means in closely spaced operative relation as a single package within the refrigerated cabinet,said casing being so arranged as to be supported adjacent to the evaporator and being effective to transmit heat between the evaporator and the temperature-responsive means.

19. In a thermostatic switch structure for controlling the operation of a refrigerator including a refrigerated cabinet and a refrigerating system, said refrigerating system including an evaporator disposed in the refrigerated cabinet, a compressor, a motor for driving the compressor and a condenser disposed outside of the refrigerated cabinet, the combination of a switch, tempera tum-responsive means for actuating the switch, means for modifying the action of the temperature-responsive means and comprising a heater disposed in heat conducting relation with the temperatur -responsivemeans and being so connected to t e motor that its heat output is varied by changes in motor load, a casing for enclosing the switch and temperature-responsive means and for retaining the switch, temperature-responsive means and modifying means in closely spaced relation as a single package withinthe refrigerated cabinet, said casing being so arranged as to be supported adjacent to the evaporator and being effective to transmit heat between the evaporator and the temperature-re 'sponsive means.

20; In a thermostatic switch structure for controlling the operation of a refrigerator including a refrigerated cabinet and a refrigerating system,

said refrigerating system including an evaporator disposed in the refrigerated cabinet, a compres- I heater disposed in heat conducting relation with the temperature-responsive means and being so connected to the motor that its heat output is varied by changes in motor load, a casing for enclosing the switch, temperature-responsive means and modifying means and for retaining them in I closely-spaced operative relation as a single package-within the refrigerated'cabinet, said casing being so arranged as to be supported adjacent to the evaporator and being effective to transmit heat between the evaporator and the temperature-responsive means.

ROGERW. HASTINGS. 

